Inflatable honeycomb



Feb. 23, 1965 E. SCHNITZER INFLATABLE aomzycoua 2 Sheets$heet 1 Filed April 23, 1962 FIG. 4

INVENTOR EMANUEL .SCH/V/TZER ATTORNEYS Feb. 23, 1965 a. SCHNITZER INFLATABLE HONEYCOMB 2 Sheets-Sheet 2 Filed April 25', 1962 INVENTOR EMANUEL SCH/V/TZER FIG. 6

fwd;

w if/M ATTORNEYS or r.

The invention'described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates generally to inflatable structures,

I and more particularly to durable, lightweight, inflatable honeycomb panel elements making up such structures, which arefoldable for transit into a compact package and inflatable, when ready for use, to assume an erected rigid configuration useful in numerous applications such as, for example, in building structures, bridge construction, orbital parabolic dish or flat disk light and radio wave reflector's, space stations, and the like.

Inflatable structures designed according to current practice generally are made up of a plurality of inflatable panelor other cellular elements; each of which is internally or externally braced or supported to insure a rigid configuration when the structure is inflated. These braces or supports add weight, which in certain applications may create critical problems, and also add bulk, which does not permit compact packaging or storage when the structure is deflated. Such bulky and weighty structures obviously are not practical for use as spatial solar energy collectors or space reflectors, for example, where satisfactory performance is directly related to the conductive or reflective surface area involved, which can be substantially independent of weight. Since weight and bulk are very critical problems in the design of payloads for carrier vehicles employed in space exploration, due to the limited capabilities of present'day rockets,'it is desirable to obtain maximum area for minimum weight and collapsed bulk in the production of certain space'objects that are to be placed in orbit about the earth. Accordingly, structures of the type contemplated by the present invention are considered quite useful in permitting ultimately large building structures, lightweight space satellites, and solar collectors,

to be stored in a compact state within a payload portion of a carrier vehicle and later erected in space to assume any predeterminedrigid configuration when inflated.

ofa new and improved inflatable reinforced panel construction. I

'A further object of this invention is the provision of a'honeycomb core element for an inflatablepanel useful in the construction of a lightweight space satellite.

United States Patent 3,170,471 Patented Feb. 23, 1965 placed between the skin members to divide the panel or envelope into a plurality of cells. The material of which the entire panel structure of the present invention is fabricated-may be a thin, lightweight, flexible plastic film or sheet which may have a thin layer of metal placed thereon to strengthen the plastic, and which may be used to reflect light and radio waves when required. The side Wall between each adjoining cell of the honeycomb reinforcing core element of the panel of the present invention is provided with at least one side wall aperture for fluid communication between the individual adjacent cells, while the external skin members are, obviously, fluid tight. Thepanel or envelope structure of the present invention is capable of being folded into a compact package occupying'approximately 5 percent of its fully inflated volume and which, when ready for use, may be erected into a rigid configuration by any suitable inflating medium such as, for example, pressurized gas, water vapor, sublimating solids, or plastic foam. Also, any desired final erected structural configuration may be formed, according to the present invention, by adhesively bonding any desired number and shapes of envelopes together, and by'establishing fluid communication between adjacent envelopes by providing therebetween a simple two-way valve element to permit expansion of an entire configuration through a single external fluid inlet or conduit. F

A more complete appreciation of the invention and many of the attendant advantages thereof will be readily apparent as the same becomes better understood .by reference to the following detailed description when considered in connection with the accompanying drawings wherein: I l I FIG. 1 is a side elevational view of, a carrier vehicle payload nose cone, with parts broken away to show packaged therein a folded reflector space satellite constructed in accordancev with thepresent invention;

FIG. 2 is an isometric view of the-inflated reflector FIG. 5 is a perspective view of one form of building structure embodying the panel element of the present invention;

FIG. 6 shows a modification of the honeycomb core useable in the panel element ofthe present invention;

and, r

FIG. 7 is a cross-sectional view of a two-way valve assembly useable to provide fluid communication between adjoining panel elements'of the present invention,

Referring now more particularly to the drawings, wherein like reference. numerals designate identical parts throughout the several, views, and more particularly to FIG. 1, there is shown a carrier vehicle payload nose A still'furtherobject of the" presentqinvention is the I provision of a fluid tight, inflatable, building panel element erectable to a rigid configuration. x

An additional object of the present invention is to provide. a new and improved structural panel or envelope.

Another additional object of) this invention is theprovision of an improved method of making a folded inflatflexible perpendicularly disposed honeycomb core element ments each having flexible outer skin members and a cone ll'having a folded expandable reflector space satellite, generally designated by the'refer ence numeral 12,

positioned therein. Satellite 12-is adapted to be forcibly ejectedbythe operation of a coil-spring 13.from nose cone 11 for spatial erection when nose conev 11 isseparated from carrier vehicle 15. A tubular conduit element 16 is connected between anopening 14 in expandable.

satellite structure 12and an inflation'medium source, such as, for example, gas bottle 18, for expandable erection of satellite 12 when separated from nose cone 11. .Suitable gas bottle 18 to seal element 16 when the inflating medium is exhausted, or when the pressure within satellite 12 reaches a predetermined maximum. 7

As shown more particularly in FIG. 2, satellite'12 is composed of a plurality of panels or envelopes 19, secured together by a conventional flexible adhesive to form the desired satellite configuration, with fluid communication between the individual envelopes 19 being provided, for example, bya two-way valve assembly generally. designated by the reference numeral 20, to be more completely described hereinafter. Alternatively, the entire configuration of satellite 12 may be formed of a single envelope when so desired. The embodiment of the invention illus trated in FIGS. 1 and 2 is'deemed particularly useful as a solar energy collector 'or space reflector for electromagnetic waves.

Referring now moreparticularly to FIGS. 3 and 4, the individual panels or envelopes 19 of satellite 12 are shown as composed of spaced, substantially parallel external ticularly suitable for this purpose is Mylar sheet or film, although other lightweight flexible plastics may be employed. Mylar isa product of E. I. du Pont de Nemours, Inc., of Wilmington, Delaware, and is formed of highly polymeric long-chain polyesters of dicarboxylic acid and.

glycol. This particular material has a high tensile and impact strength,'and.rem'ains flexible'and stable over a ment 24 is composed of a plurality'of perforated parallel spacer sheets 25 perpendicularly disposed between and bonded by means of a conventional flexible adhesive such as, for example, a low temperature thermosetting resin 29, influid tight relationship with skins21, 22, as well 'as with peripheral wall 23 at the points of contact therewith, to form a plurality of rectangularly shaped compartments designated by reference numeral 26; A sheet of redoubled sinuous material 28 having half-lengths connected one to the other at confronting nodal points .divideseach rectang'ular' shaped compartment 26 into a plurality of honey:

comb cells 27. The individual honeycomb cells 27*are formed by bonding with adhesive 29 half-lengths of sheet "By selecting the points of contactthat sheet 28 makes with the other structure, the cross-sectional area of honeycomb cells 27 may bereadily controlled. A sheet 28 may .b'e preform'ed in any desired sinuous shape andmay thus range of temperatures from. minus degrees- C. to degrees C. To provide a final rigid configuration, as well as to provide a'reflective surface on the Mylar film, a thin continuous lightweight metallic coating such as, for example, aluminum; is deposited overone or both sides of the Mylar film. This'metalliccoating may-be provided in any conventional manner such as, for example, by vapor deposition, or bybondin'gsone or more metallic sheets to one or more sides of the plastic with aisuitable adhesive to thereby form either atwo or threeply laminated structure. Laminated materials of this type have an inherent stiffness, althoughgthey are readily workable into desired shapes. Further, such materials, uponbeing subjected to loading developing tensile stresses. therein exceeding the elastic limitof the metallic. layer but less than the ultimate tensile strength thereof, will. develop a substantial rigidness due to permanent set in the' metallic layer. It has been found that micrometroidpuncture of inflated structures may permit rapid escapeofthe inflation medium therefrom. Under these circumstances'such inflated structures, in the absence of the honeycomb internal bracing configuration of thepresentinvention, may collapse despite the permanent set developed by the metallic layer or layers of the laminated material. underithe influence of solar pressure- However, when the honeycomb reinforced 5 panel members of the present invention are utilized in aspace'vehicle, the materialIZS in the wall of each individual honeycomb cellY27 develops permanent set'and resists any tendency of either'skin 21 or skin 22 to collapse. Tn addition to the forces exerted on skins 21 and 22 by material 28, additional similar forces are exerted on the'inn'er surfacesof. the skins to prevent collapse thereof by parallelspacer elements 24. This corn bination o'fiinternal forces in panel 19 results in the. mainprovide honeycomb-.cellsi27 of triangular, square, circular,

or other polygonal cross-sectional shapes, as desired.

-Alternatively, referringnow to FIG. 6, the honeycomb" cells may be formed individually and :bonded. to'each other and to spacer sheets 25' by flexible adhesive 29,

' which is applied to the surface of skins 21 and 22 prior to assembly of spacer sheets 25 and honeycomb cells 27. The external: surface :of both end portions of eachintenance of a predetermined final configuration for each.

individual panel in an assembly, such as satellite 12 after its inflation, even ifIthe inflating medium. is subsequently removed'oriescapes;

FIG. 5 of the dra'wings illustrates a collapsible building structure, generally designated by the referencenumeral dividual cell wall may also be coated with additional I adhesive 29 to assure an adequate bond between each individual cell, when so desired, although it isapparent 1 thatjsome adhesive will normally flow between the individual cells during curing or setting of the adhesive on skins 21 and 22 afterassemblyof the panelor envelope.

7 The assembly of the panel by inserting individual preformedcells is required when the 'cells are of circular cross-sectional configuration, andthis process may also be desirable for assembly of other cell configurations, under some circumstances. I

7 Each individual cell 27 in the final assembly of a panel or envelope 19 is provided with at .least one aperture" 31 v in the side wall thereoffor fluid communication with each "adjacent cell. jApertures 31 may be formed in sheet 28, either priorfto'assembly-of cells27 or after the cells; are formedp. Also, referring once again toFIGS. 3 and6, j it will be seen that apertures or perforations 32 in spacer. fsheets 25 provide fluid communicationbetween respective rectangular shaped compartments 26.

The various skin sheets for panels or envelopes.19,s and'the honeycomb .core' elements therefor, are all pref- 'erablyforrned from the'samexstrong, flexible, and light iwe'ight material. One such material'that has proved par- 75.

for structure 33;

[33,Iuseful, for example, as an aircrafthangerr Building '33 employs apluralityof panels orenvelopes '19, as :herea inbefore described, bonded together bya suitable adhesiver Fluidcornmunication is established between ad-' joining-panels 19 as, for example, through valve assem:

blies 20.. Ground engaging flaps 34,.having aplurality of spaced openings 36 therein:througliwhichground stakes or anchors may be passed, are bonded by a suitable adhesive to end wall portions of envelopes 19. A

plurality of guy wires 38, when required, may be con- -nected to ring members 39, both internally and externally of structure 33, and to ground stakes'37, as additional supports for structure 33 for withstanding wind forces.

Also, if desired, additional panels of suitable configuration, not shown, maybe bonded to peripheralfwall 23' of end panels 19 to provide front and rear end walls for thebuilding structure 33. Although building 33 isshown as having a continuously-curved roofsimilar toithose of Quonset huts, other building configurations, obviously, may be formed within thescope of this invention by selecting other desired'shapesfor panels 19. Further, where a more permanent, building is desired, it is within'the scope p of this invention to employ a plastic foamor any other suitable initially 'flowable material as the inflating medium The thickness ofeach individual panel19 jrnay be easily controlled by selecting the desired height-of the honeycomb cells 27 inadjacent rectangular compartments 26 while providing the appropriate varying height for peripheral wall 23. The height-of. the individual 'honeycomb cells may vary from a fraction of an inch to several feetdepending upon the type of final configuration desired, and the environmental conditions expected where the structure is to :be used. The width of each panel 19 is, obviously, controlled by the width or external surface I area of skins 21 and 22.

Referring now to FIG. 7, one form of suitable valve assembly 20 for providing fluid interconnection between two adjacent panel members 19 consists of a somewhat rigid and slightly flexible tubular needle 41,- having'a thin flap 42 of plastic or othersuitable slightly flexible material securely positioned transversely thereto at about the center thereof. When it is desired to secure two or more adjoining envelopes 19 for fluid communication, needle 41' is inserted through the adjacent peripheral walls 23 ofenv'elopes 19, and fia'p42 is securely bonded to the respective peripheral walls by means of asuitable adhesive.

To assemble a panel or envelope of the present invention, referring now back to FIG. 3, skin 21 is placed fiat over a' work table or other suitable area, and a suitable (adhesive coating 29 applied tothe entire exposed'surface.

Overlap sectionsof, peripheral wall or skin 23 are then bonded toskin 21 to form an open box-type configuration. Perforated spacer sheets 25, which are cut slightly larger than the width of skin 21 andwider than the height or peripheral wall 23 "to provide an overlap at the ends and-sides thereof, arenext bonded at spaced intervals to peripheralwall 23 and skin 21; thereby dividing the entire area'into a plurality 'of rectan'gularly shaped compartments 24. A sheet of material '28 of the same height I as peripheral wall 23, but, having considerable length, is

then sinuously folded along a lengthwise portion thereof and bonded at spacedintervals to the 'entire length of one surface of a firstspacer sheet 25,.with-the portion of sheet 28 between theindividual. bonds forming with spacer I sheet 25..a plurality of cells of substantiallytriangular cros's sectio'nal configuration. Theexcess of sheet 28 extends along the edgeof peripheral wall23 toja second spacer sheet 25 and then is'sinuously folded along the remainder of. the length thereof and bonded to; a,-second perforated spacer sheet'25 at equally spacedintervala'.

- forming a second set of cells having substantially triangular cross-sectionalarea.

angular cells are'adhesively joinedto completethe cellu- The apexes of both sets of trilar structure ofone compartrne nt within the panel 19. 'lhis'procedure is repeated until the entire'panel core 'c'onfiguration is complete, at whichtime skin 22 with an adhesive 29 coated on'one'. s'urface'thereof is secured to seal the assembled structure in fluid tight relationship,- with the exception of conduit 14' which may extendtion or apertures within spacer sheets 25 and sheet ma terial 28 which, together, form the individual honeycomb cells ,27. A vacuum pump may be attached to conduit 14 to'aid in removal of any trapped air in the panel during fabrication. When it is desired to use more than one panel or envelope 19 in forming a particular configuration, the panels are placed in fluid communication with each other by suitable means, such as two-way valve as semblies 20, with the adjacent peripheral wall or skins 23 being penetrated by opposite ends of hollow needle 41 and adhesively bonded to each other and tothin plastic flap" 42 of valve assembly 20. The overall size of flap 42 is controlled so as to be less than the height of peripheral wall members 23 to effect a smooth surface seal between the adjacent peripheral wall members." -The assembled Any air trapped within the core duringwassembly is bled off during the folding operation through conduit 14 byway of the individual perforastructure may then be placed in a low temperatureiovenw to effect curing of the low temperature thermosetting .resin adhesive 29 when this type adhesive isemployed.

The-physical characteristics of the material making up the panel permits the complete structure to be substantially flattened and folded, end to end, and side to side,

into a compact package constituting avolume of only approximately 5 percent of'the total inflated volume of the panel. Although this folding creates; numerous wrinkles,

the wrinkles are completely removed when the structure sheet material 28 may be divided into honeycomb cells within two or more spacer sheets and assembled as units to the adhesive'coated skin 21, within the confines of peripheral wall 24, and then covered by skin 22.

Also, as mentioned heretofore, and as shown in FIG. 6, the honeycomb cells can be formed and positioned within the compartments formed by spacer sheets 25 individually, When'so desired. t i

* Obviously, many modifications and'variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may beprac ticed otherwise than as specifically described.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

- 1; An inflatable envelope panel, comprising: aflexi-ble internal skin, a flexible external skin, and a flexible peripheral wall member interconnecting said internal skin closed envelope, each said internal skin, external skin,

peripheral Wall, and said bracin'gcore being constructed of a metal-plasticslarninateand having the inherent physical property characteristic of developing sufiicient tensile stress therein when said envelope is inflated to resist subsequent envelope collapse; and means forintroducing an inflation medium intosaid envelope. r

2 An inflatable panel, comprising: a flexibleinte'rnalskin, aflexible external skin-spacedfrom'said internal.

skin, and aflexibleperipheral wall merriber interconnectingl said skins "to form an enclosed space; a flexible honeycomb bracing core element disposed within said en- 7 closed space and attached to'the inner surfaces of said skins. and said peripheral wall member, saidhoneycornb core element including a plurality of perforated spacer elements perpendicularly secured to said inner surfaces-of said skinmembers and said pe'ripheral wall and dividing the space bounded bysaid skins and saidpcripheralwall members into a plurality of substantially, re'ctangularly shaped compartments, each'said rectangularly shaped compartment being divided into a plurality of honey comb cells by a sheet of material bonded to at least one of said perforated spacer elements at spaced-intervals thereon; and means for introducing an inflation medium posed perforated spacer elements dividing said core elcmerit into a plurality of substantially rectangularly shaped compartments, each fof said rectangularly shaped compartments including cell wall means dividing the cells perpendicularly disposed with respect to said skinmembers, each; honeycomb cell being'provided with at.

least 'one'wall aperture for fluid communication with each adjacent cell; and means for introducing an inflation'medium into each of said inflatable panels. 4. An inflatable structurecomprising: a flexible internal skin; I i .a flexible external skin, I r v a flexible peripheral wall member interconecting said internal "skin to said'external skin in spaced relationa ship toform an enclosed envelope;. I aiflexible brace/positioned Within and secured to the inner surfacesof said enclosed envelope; said flexible brace including:

(a) a plurality of spacer elements perpindicularlysecured to the inner surfacesof said skins and said peripheral wall member for dividing it a said valve assemblygincluding I i 1 I a) a unitary tubular needle; and

A cured to said needle intermediateithe fends thereof, said {flap being adhesively bonded to adjacent peripheral wall members of isaid Vjux- I vtaposed panels, P e

and

a conduitconnected: between atleast one of said pan- I els and a; central sourcezof inflation medium, I

surface thereof,= cornprising:

said enclosed envelope into a plurality of com- I partments, and a (5)1 a sheet of redoubledsinuous material having half-lengthsconnected one to the other at confronting nodal points 'in each said compartment tov divide each compartment intoa plurality of honeycomb cells, 1 A 5 inflation means for inflating said envelope with. an,

inflation medium, 1 I 7 each of said internal skin, external skin, peripheral wall and said flexible brace being constructed of e a metal-plastics laminate,

said laminate having the inherent physical property characteristic of developing-tensile stresses therein,

upon said envelope being inflated to its final configuration; suflicient to-resistcollapse of said en-' velope uponsubsequent removal of saidinflation I medium.' r, I 5. The inflatable panel of-claim 2 wherein: I I I a'metal-plastics laminate material is employed for each of said internal skin, saidjexternal skin, said periph-' veral wall member,. .said perforated spacerxeleme nts and said sheets oftmaterial forming saidhoneycomb;

cells,

' said metal-plastics laminate -material having the inherent physical property characteristic of developing a permanent set therein when inflated by said inflation medium to be stressed ibeyond the elastic limit thereof tea-pointless than its ultimate tensilei;

strength fl II 1 I 6; The expandable structureof claim 3 wherein said said inflatable panels includes:

' atwowayvalve assembly interconnected"between the I I I I I I H I V I THARRISON R IMOSELEY, PrimaryfExqmiizei-i;

adjacent peripheral; walls of juxtaposed panels jto meansfor introducing an'inflation' medium into each of;

ship to form an enclosed envelopeg} v. I 1 I V a flexible brace positioned within Gand-secured tojthe inner surfaces of said enclosed 'envelope, a; said flexible brace including: I i S (a) a plurality of .spacer'elements perpendicu- -lar1y secured to the inner surfaces of said skins,

and fsaid peripheral Wallmember" for dividing}- saidfenclosed envelope into a plurality of corn- I partm'ents', and I a I i (b) a sheet of redoubled, sinuous'mat'erial hav I ing half-lengths'connectedone to the other at confronting" nodal 'pointsin each said comparti. ment to, divide;ea ch' compartment into a plutrality of honeycomb cellsl 1 1 References fiitedb y the E Xamili1 I I UNITED-STATES, PATENTS I I II 468,455 279.2 Giessmann -1-135 1 1,754,784 4/30'-B01sodi' i; 15 6292 1,920,961; 3/33 ,An'ders on" 15'6 292- 42,477,852, "8/49 Bacon 15 6 i 292'X- 2,543,879 3/51 steamy '156292 X 2,698,620? 12/54 Phane 1 2,702,580, 22 55, Batemanr '16- 1'165' j 2,718,014] 9/551 Mizrach'etfah: -;l35 1 I 2,812,769 11/57- Schaefer et'al. -13 51 I 2,819,724 1/58 Barlger: 135 -1 2,888,675 5/59; P'rfatt et al. 343-915 K 2,895,490 7/59 Dimond 1 135-5-1 V 2,934,075 4/60 Richardson et al. 135-7 1 2,977,596 '3/61] Justice i343+915 f i I FQ REIGN PATEN Ts II 1 1,194,773 5 /59 France; 1

a flexible internal skin,f I I I I a'flex-ibleexternal skin, 1 5 L A e internal skin to said external skin in; spaced relatione f y w 

1. AN INFLATABLE ENVELOPE PANEL, COMPRISING: A FLEXIBLE INTERNAL SKIN, A FLEXIBLE EXTERNAL SKIN, AND A FLEXIBLE PERIPHERAL WALL MEMBER INTERCONNECTING SAID INTERNAL SKIN TO SAID EXTERNAL SKIN IN SPACE RELATIONSHIP TO FORM AN ENCLOSED ENVELOPE; A FLEXIBLE BRACING CORE ELEMENT POSITIONED WITHIN SAID SECURED TO THE INNER SURFACDS OF SAID ENCLOSED ENVELOPE, EACH SAID INTERNAL SKIN, EXTERNAL SKIN, PERIPHERAL WALL, AND SAID BRACING CORE BEING CONSTRUCTED OF A METAL-PLASTICS LAMINATE AND HAVING THE INHERENT PHYSICAL PROPERTY CHARACTERISTIC OF DEVELOPING SUFFICIENT TENSILE STRESS THEREIN WHEN SAID ENVELOPE IS INFLATED TO RESIST SUBSEQUENT ENVELOPE COLLAPSE; AND MEANS FOR INTRODUCING AN INFLATION MEDIUM INTO SAID ENVELOPE. 